Electrical switch



Dec. 15, 1931.

H. B DWIGHT ELECTRICAL SWITCH -Filed Dec. 19, 1928' Patented Dec. 15, 1931 PATENT," OFFICE HERBERT BRISTOL DWIGHT, or WINTER-P, MASSACHUSETTS ELECTRICAL swrrcn Application med December 19, 1928. Serial No. 327,125.

The present invention relates to electrical Switches and more particularly to high voltage isolating switches commonly known as disconnecting, switches.

'Disconnecting switches are ordinarily em-,

ployed for the purpose of occasionallyisolating the line from the power equipment and are not intended to break a circuit carrying a heavy load. Because of the fact that they are not frequently operated, they may be of quite simple construction, comprising merely a pivoted blade cooperating with a hinge and a jaw, the whole switch being unenclosed and for reasons of safety, being usually placed at a considerable height above the floor. The

ordinary type of disconnecting switch possesses the disadvantage that it is Subject to forces which tend to blow it open. 7 These forces arise from the interaction of the ourrent in the blade with magnetic fields set up by the currents in the hinge and jaw and in the associated conductors. These opening forces are normally resisted by the frictional engagement of the blade with the hinge and -jaw, which is sufiicient under normal conditions to hold the switch closed but under abnormal circumstances, such as a high overload or a short circuit, the forces rise to such values as to overcome the frictional resistance. Inasmuch as these switches are not intended to act as overload circuit breakers, such accidental opening is highly undesirable, both from the standpoint of the difficulty of again closing the switch in its relatively inaccessible position, and also of the injury likely to be caused to the switch by the intense arc formed by the breaking of a circuit carrying a high current. It has been proposed to prevent accidental opening of the switch under abnormal currents by the provision of mechanical devices for locking the blade but these have the disadvantage of complicating the construction of an otherwise simple piece of equipment and consequently increasing the expense and the necessity for repairs.

The object of the present invention is to provide a simple and inexpensive disconnecting switch in which there is no inherent tendency to open the blade, whereby the switch remains closed even under excessive loads. VV'th this object in view, one feature of the present invention comprises a switch and an associated circuit therefor in whichthe magnetic fields set up by the currents external to the blade are so disposed both in ositionand direction relative to the blade t at no forces sufi'icient to open the blade are applied thereto. From calculations and exp'eriment on ordinary forms of disconnect m ing switches, I have discovered that the principal force tending to open the blade 'is caused by the currents in the hinge and jaw,

which currents are at right angles to the current of the blade and which therefore set up 5 magnetic fields cutting the current carrying blade in such a direction as to apply 0 enin forces thereto." The magnitudes of Sue forces depend upon the strength of the current and also on the length of theright angle portion through which the current passes to the blade. The conductors which connect with the hinge and'jaw at the base of the switch and which lie parallel to the switch blade, also set up fields which have someef- 7 feet on the blade but the forces thus set up in the usual circuits are not ordinarily of great importance compared to the. forces arising from the right angle currents in the hinge and jaw. 7

According to the present'invention, the switch comprises a blade, blade engaging members including a hinge and jaw, together with conductors forming a circuit eX- ternal to the blade and connected to the blade 5 engaging members at approximately the same surface of contact as the blade itself, whereby; the current enters directly from the external circuit into the blade without traversing the right angle portions of the hinge or aw. In the preferred form of the invention, the blade and the conductors of the external circuit have substantially coincident axes, so that no forces in any direction are applied to the blade,

In the accompanying dr'aw1ngs,Fig. lis

a side elevation of a switch in which no Substantial forces in either an opening or a clos ing direction are set up; and Fig. 2 is a plan view of the switch shown in Fig. 1.

In the illustrated construction, a pair of conductors 32 lead to the hinge 33 and are suitably connected thereto and a similar pair of conductors 34 are attached to the aw 35. The conductors are held apart by spacers 36 placed at a distance from the hinge and jaw in order to permit springing of the blades of the hinge and'j aw in opening or closing the switch. The separate conductors of each pair may be connected together beyond the spacers i de ired- Th bla e 3:7. is pivoted at one end to the hinge, and is adapted to engage the jaw35 at the other end. The hinge and jaw are mounted on a suitable base 10.

The conductors are therefore connected to, the blade engaging members, over surfaces practically coextensive with the surfaces of engagement 'of the blade therewith, that is to. say, the blade and the conductors of the circuit'external t0 the blade are so, arranged that the current enters directly into the blade withonttraversing any rightangle portions of the hinge and jaw. As shown in full lines in Fig; 1, the conductors and the blade. are disposed in the same line, that is, they have coincident axes when the switch is closed. From the symmetry of the constrnction, it is evident that no. unbalanced force can act on the blade, either in opening or closing: direction. Describing the construction in another way, the angle between the center line of the blade and the center line of the conductor is 180 as measured from the blade to the conductor in the direction of the closing movement of the swit h, when the switchis closed.

A modified form of the construction is,

indicated in dot-and-dash lines shown the conductor 38. disposed from the blade at an angle slightly less than 180, structure, although not completely eliminating all forces,'"brings about an opening force, of such small magnitude as to be. practically negligible The construction may be preferred for mechanical reasonsv to that shown in full lines. In any case, the conductor'is. connected directly with the blade engaging surface of the hinge or jaw so that the rightangle currents which would set up. opening forces are entirely eliminate-d.

It Will be understood that although the invention has been described as embodied in a switch having its hinge and jaw mounted This 001 lQA disconnecting switch comprising a single blade, blade engaging members including a hinge to which the blade is pivoted and a jaw, conductors connected with the blade engaging members and having substantially coincident axes with the blade to permit the existence of no forces to open the blade underheavy currents.

2. A disconnecting switch comprising a single blade, blade engaging members inl ding a hing ta wh ch the bla e i pivoted and a jaw, conductors connected with the blade engaging members over surfaces substantially co-extensive with the surfaces of engagement of the blade therewith and havg ub t n ially c ncident. axes wi h t blade When th switc i closed. o. permit. the.

x tence of. no, for s to. 211 .1 the b ade. under heavy currents.

I te t mony where fl' hav signed my ame to this ne ifi atiolr.

HERBERT BR STOL DWIGHI on a base 10, this mounting is to be consid-.

ered as diagrammatic only, and where insulation against high voltage. is necessary, the mounting of the hinge and jaw on separate insulators may be preferred. Alsoit will be understood that the blade is not limited to the single strap. but may comprise a plural ity of parallel connected straps according tov any usual or preferred construction.

-Ha ving thus described the invention, what is claimed is; 

